The principle of obtaining amines starting from an olefin, hydrogen, carbon monoxide and a primary or secondary amine is known. Various techniques embodying this principle have been described using catalysts of various kinds.
Early work in this field taught that aliphatic acids may be obtained by reacting carbon monoxide with an olefin and steam and that ammonia may be reacted with carbon monoxide to produce formamide. U.S. Pat. No. 2,422,632 (1944) appears to be the first work to suggest a process by which an olefin may be reacted with carbon monoxide and ammonia or an amine having replaceable hydrogen to form an amide or amine.
U.S. Pat. No. 2,497,310 (1946) defined a process for the synthesis of aliphatic amines which consisted of introducing carbon monoxide, hydrogen, a compound from the group consisting of ammonia and amines having at least one hydrogen attached to amino nitrogen, an unsaturated compound containing a non-benzenoid double bond between carbon atoms, and a catalytic quantity of cobalt metal, into a pressure resistant vessel and heating the resultant mixture within the range of 50.degree.-350.degree. C. under a reaction pressure in excess of 50 atm, whereby a reaction product containing amines is produced and thereafter separated from the reaction product.
In Shell International Research Maatschappy B. V. Neth. Appl. No. 6,405,802 Nov. 30, 1964; U.S. Pat. No. 3,234,283 (1966) tertiary amines are obtained in improved yields and at lower pressures than prior process by treating CO, hydrogen and a secondary amine with a C.sub.10 -C.sub.13 olefinic mixture in the presence of a cobalt carbonyl-trialkylphosphine catalyst.
U.S. Pat. No. 3,513,200 (1970) covers the utilization of Group VIII metal complexes bearing a biphyllic ligand such as a phosphine and, optionally, these complexes may contain a metal hydride complexed with CO. There can be added, as an adjuvant, poly(hetercyclo)amines. The reaction is realized at a temperature between 50.degree. and 200.degree. C. and under a pressure ranging from 5 to 300 atmospheres. A significant proportion of aldehydes is obtained and the selectivity to amines is still in this case very moderate.
In a paper by Iqbal published in Helvetica Chemica Acta, Volume 54, pages 1440 to 1445 (1971), as well as in U.S. Pat. No. 3,947,458 (1976), the catalytic aminomethylation of olefins is described employing a rhodium oxide catalyst, an iron carbonyl catalyst and a mixed rhodium oxide/iron carbonyl catalyst. (Rhodium carbonyls form during the reaction.) The overall reaction is described as follows: ##STR1## The mixed rhodium/iron carbonyl catalyst of Iqbal is said to be superior to the rhodium carbonyl catalyst alone and to the iron carbonyl catalyst alone. However, this mixed rhodium carbonyl/iron carbonyl catalyst is believed by Laine (U.S. Pat. No. 4,292,242) to be less selective and has other disadvantages, among which are the following: The rhodium carbonyl/iron carbonyl catalyst is not stable and is prone to decompose; its use results in carboxy amide by-products; and it reduces some of the intermediate aldehyde to an alcohol. Also, in the case of an olefin having a terminal vinyl group, --CH=CH.sub.2, a considerable proportion of the amino product is branched chain, thus ##STR2## rather than straight chain, thus EQU --CH.sub.2 --CH.sub.2 --CH.sub.2 N&lt;
The straight chain products are more important commercially.
U.S. Pat. No. 4,096,150 (1978) discloses a process for the manufacture of tertiary amines wherein an olefin, hydrogen, CO and secondary amine are reacted in the presence of a coordination complex catalyst of a Group VIII metal and a ligand, the donor atom of which is oxygen, nitrogen or sulfur.
In J. Org. Chem. 45 3370 (1980), Laine, et al. describe the results of their studies on the aminomethylation reaction using a variety of Group VIII transition-metal carbonyl catalyst precursors.
U.S. Pat. No. 4,292,242 states that the object of its invention is to provide improved methods of aminomethylation which are more selective and lead to fewer unwanted by-products such as alcohols and carboxy amides. A further object mentioned was to provide a more stable mixed carbonyl catalyst, the use of which would result in higher yields of the desired amines. Here the claimed catalyst is a mixed ruthenium carbonyl/iron carbonyl in a suitable solvent. Again, this process leads to a formamide by-product.
In J. Org. Chem., 47, 445 (1982), Jachimowicz, et al. discuss the various approaches which have been used to attempt to devise a one-step, efficient and general conversion of olefins to amines. Among the catalysts used in processes devised by various people have been iron pentacarbonyl, rhodium oxide, ruthenium/iron carbonyl and iridium catalysts. The discussion in this article examines the feasibility of various aminomethylation syntheses.
In prior processes in the art by which aminomethylation takes place, the reaction must often take place at high temperatures and/or pressures, the olefin conversion and selectivity to the desired tertiary amines is not as high as desired, unwanted by-products such as formamides are often formed, and a high degree of desired linearity is not achieved. Additionally separation of the desired product from by-products is often difficult, expensive and time consuming; distillation as a separation technique can be relatively difficult because of the high boiling point of the products.
It would be a considerable advance in the art to devise a system for producing secondary and tertiary amines from CO, hydrogen, olefins and primary and secondary amines by an aminomethylation process which results in a product with a much higher percentage linear amines. The resulting alkylamines are useful as surfactants or surfactant precursors. In such applications the linear products are more desirable and, as stated, it would be a considerable advance to provide them in higher yield. In addition, it would be an advance over prior art to devise a process which proceeds under milder reaction conditions, forms fewer unwanted by-products such as formamides and affords easy and efficient separation of the desired product from by-products and catalyst.